The present invention relates to a liquid flow regulator. In particular, the present invention is suitable for use as an adjustable-rate flow regulator utilizable in an infusion set.
WO 96/03166 (Baxter) discloses a fluid flow regulator provided with a housing and a flexible diaphragm clamped in the housing along its periphery, prebiased so that in its state of rest it assumes an arcuate shape, prestressing the diaphragm towards the outlet, thereby reducing its sensitivity by causing the diaphragm to lose its elastic properties, especially in the range essential for improved control sensitivity required for low rate flows such as those normally used for intravenous administration of fluids.
In U.S. Pat. No. 5,421,363, there is described an adjustable- rate flow regulator with a greatly enhanced accuracy and improved repeatability, over similar prior art flow regulators. This flow regulator is suitable to operate at low dripping rates reaching, for example, 2 ml/hr, at a low pressure drop across the diaphragm of e.,g., only 40 cm of water, in view of a restricted pressure head. The regulator functions as a negative feedback closed loop control system. Due to the relatively long flow attenuating passageway associated with the feedback portion of the system, as well as due to other time constants of the system during operation, the latter tends to become inaccurate, instable and to oscillate vigorously about its set operating flow rate.